STRUCTURE AND IDENTIFICATION OF ROOT BARK OF QUERCUS-ROBUR L

The root bark structure of Quercus robur L. was analysed at different stages of root development and compared to the structure of stem bark. Root bark thickness varied considerably between different roots. Scle reid quantity decreased with increasing distance from the stem, which means it increased with age. Visible growth increments diminished with increasing distance from the stem. In lateral roots crystal quantity decreased with increasing distance from the stem. In lateral roots sec ondary phloem fibre length, sieve tube member length, and sieve tube d iameter showed no regular trend. There were only a few basic structura l differences between root and stem bark. The zone of cell differentia tion (cell expansion, lignification) was wider in root bark; sieve tub e collapse was delayed. In lateral root bark fewer sclereids were form ed. The first-formed periderm often originated from deeper cell layers . Thus, primary elements were lacking after periderm formation. In roo t bark the phellem cell walls were of equal thickness. Thus, phellem l acked visible growth increments Root bark phellem cells were slightly larger. The root phelloderm was more distinct. The secondary phloem fi bres were slightly shorter than those in stem bark. Sieve tube members of stem and root bark were of similar length and diameter. The qualit ative bark anatomical characters of oak root bark are suitable for roo t identifications. Due to minor structural differences between root an d stem bark the characters must be used with care.